Network analyzers are devices utilized to connect to communications networks, particularly packet networks, which monitor the signalling state and traffic flow of communications on the network. For example, when digital packet transmission is utilized, a monitor will detect each packet which passes the analyzer connection point and will reproduce some or all of the information being transmitted in its memory. Typically, network analyzers attach a timestamp to each packet received so that information about the number and type of packets passing a given point can be gathered.
The sophistication of networks is growing rapidly. Recently, full service digital networks have been developed which can provide, among other things, video on demand service to a user.
The invention is applicable to a full spectrum of networks. However, the invention will be disclosed in the context of a full service digital network to illustrate only one of several concrete examples.
The operation of such a full service digital network will be described in connection with full service network embodiments depicted in FIGS. 1 and 2. When a subscriber desires to watch television or engage in one of the other services provided by the network, the subscriber activates a set top box known as a digital entertainment terminal (DET) 150 either manually or by a remote control to "turn it on." Turn on may either be an actual power-up or an activation of a DET already powered up. When the DET is turned on, a message is sent over the subscriber link to an optical network unit ONU (151) which services the DET. ONU's are typically located in concentrator bays. The ONU 151 knows the port associated with the DET which has been activated by virtue of either explicit addressing or by virtue of the time slot position of the incoming data. The ONU then initiates a connection to the Level 1 gateway 154 either by way of a distribution component such as digital cross connect switch 152 and ATM Video Switch 155 or by way of ONU 151 or its concentrator and the X.25 network 153. The level 1 gateway then downloads a menu to the DET which has been activated. The menu typically includes the services available to the subscriber at that DET. The subscriber selects a particular service to be invoked and a selection message is sent from the DET 150 to the ONU 151 where it is routed to the level 1 gateway 154. The level 1 gateway knows, by virtue of addressing information applied by the ONU, the ONU number, ONU port number and time slot associated with the DET which requested service. If the service requested is a premium service, such as video-on-demand, the level 1 gateway initiates a connection to an information server (IS) 157 via the level 2 gateway. It notifies the IS of a billing number associated with the subscriber. The server then notifies the level 1 gateway over the reverse path whether or not service is authorized to the subscriber. If service is not authorized, the level 1 gateway will provide a message to the DET and, depending on circumstances, may provide the DET user with an opportunity to subscribe to the service.
If the connection is authorized, the level 1 gateway notifies the PVC controller 156 to activate a permanent virtual circuit between a server port identified by information returned from the server and the port number of the DET desiring the service. Once a communication session is established between the server and the DET requesting service, management of the communication session is transferred to the level 2 gateway 158 of the server and the set up connections are broken down between the level 1 gateway 154 and the DET 150 and between the level 1 gateway 154 and the server 157.
If the subscriber desires to change services, the subscriber may terminate the session with the level 2 gateway and then initiate a new session for establishment of the new service by way of the level 1 gateway.
FIG. 2 will be utilized to explain the operation of the full service digital network in another embodiment utilizing an intelligent access peripheral (IAP). As before, when a DET 160 being serviced by an IAP 161 is turned on, a message is sent to the IAP over an upstream Asymmetric Digital Subscriber Line (ADSL) signaling channel. The IAP then initiates a connection to the level 1 gateway which is directly serviced by a port on the ATM switch 162 and the level 1 gateway downloads a menu as before. When the subscriber desires a particular service, and selects that service, a message is sent to the IAP 161. The IAP checks the class of service authorizations contained within a user profile/access management unit to see if the service is authorized to the requesting subscriber. If the service is authorized, the request for services is passed on to the level 1 gateway.
At the level 1 gateway, the particular service selected is identified and a message is sent to the IS 167 over ATM video switch 165 and multiplexer 169. If the server is willing to accept the connection, the server notifies the level 1 gateway over the reverse path and the level 1 gateway specifies the port numbers of the server and the DET to be connected via ATM switches 165 and 162. Once a direct connection between the DET and the IS is established, session management is transferred to the level 2 gateway 168 of the information service provider and connections utilized to set up the call over the ATM switches between the DET and the level 1 gateway and between the level 1 gateway and the ISP are broken down in favor of the direct connection between the DET and the ISP.
As these two examples show, very complicated interactions occur between a user and various components distributed across a full service network. One of the problems associated with design and construction of a network intended to provide functionality never before implemented is that the sizing and capabilities required of the equipment is initially available only as a set of assumptions in the designer's mind. As the network is actually implemented, difficulties arise and problems must be faced which prevent one from creating an efficient system. Since the cost effectiveness of implementations are highly dependent upon the type of equipment purchased, the cost of an overall implementation may become economically infeasible if equipment is sized too large or may become unsatisfactory to a user if sized too small.
To help in designing an economically balanced system, computer simulation is frequently employed simulation permits the designer to experiment with various scenarios without having to invest the money for the equipment in order to establish the efficiency and cost effectiveness of the system and the service levels to be provided to a user.
The problem with simulation is that, in many respects, it is an art form. The intuition of the person building the simulation is utilized to make a variety of implementation decisions which can affect the overall predictions of a simulation model.
To prevent making errors which can be very costly, it is desirable to validate a simulation model. Typically, a number of techniques may be employed to validate a simulation model. One of the more common is to construct a test system and permit users to interact with the test system to determine how users will utilize the system under actual conditions. A great deal of useful information can be obtained through feedback from the users of the test system about what features need to be changed and how the responsiveness of the system impacts the user's work.
When building a nationwide full service network such as described in conjunction with FIGS. 1 and 2, implementation can be expected to cost billions of dollars. However, cost for a local test installation would be very reasonable in comparison. To make design decisions for a nationwide network, one would desire to use a simulation of the fully deployed network to validate that simulation against data collected in the test environment of how the various network elements will perform. With reasonable care in addressing issues of how to scale up a local model to a national one, a test bed validated simulation model will provide much better information about a fully deployed national network than one using only a simulation designer's estimates.
Even a limited test bed of a full service network, may require many miles of wiring plant with devices distributed over the area of the test. Even though one can build individual device models by testing devices in isolation, when devices interact with other components of a network, the results can be quite different. Therefore, it is highly desirable to be able to measure the performance of individual network elements under actual operating conditions of a test bed.
Individual network monitors are unable to provide the kinds of information needed to achieve this.
First, individual network analyzers have only a single point of connection to the network. Therefore, network analyzers of the prior art are unable to trace information flows through multiple steps and devices utilized in the network. Further, a single network analyzer is unable to measure device latencies and the statistics of device latencies under conditions when one kind of input comes in one side and a different type of input emerges from the other side of the device. Typically, a simulation designer will estimate average service request arrivals and assume that they are Poisson distributed. Similarly, the service times for the device are generally assumed to be exponential in the absence of other information.
An individual network monitor provides a myopic perspective of network performance which tends to miss important relationships, especially multivariate relationships, which may be critical to overall network performance. Further, network analyzers have a limited graphic display capability to use and make visible such relationships. Another disadvantage of prior art network analyzers is that they have a limited capability to handle different forms of data. For example, turning to FIG. 1, the arrangement of data received from a DET 150 is different from information provided to ONU 151. That, in turn, has a different protocol and is formatted differently from the information provided to X.25 network 153. The protocols utilized in the connection between the level 1 gateway 154 and ATM video switch 155 are likely different from those utilized to provide information from the level 1 gateway to PVC controller 156. In short, as information traverses a sophisticated network, a variety of communication protocols are utilized which result in a variety of different data formats.
Accordingly, one advantage of the invention is the integration of network performance analyzers which can monitor information at a plurality of points in the network.
Another advantage of the invention is the ability to trace data through multiple points in a complex distributed network.
Another advantage of the invention is the provision of methods and apparatus for measuring latency and statistics of latency for individual devices.
Another advantage of the invention is the provision of a network performance analyzer which views network performance from a multiple viewpoint perspective which can highlight complex relationships.
Another advantage of the invention is the provision of a graphical display of complex multivariate relationships.
Another advantage of the invention is the provision of a network performance analyzer which can follow information flows across multiple portions of a network in which different addressing protocols are utilized.